Use of ion pair amphiphile as an alternative of natural phospholipids in enhancing the stability and anticancer activity of oleanolic acid loaded nanostructured lipid carriers

Nanostructured lipid carriers (NLC) comprising soy lecithin (SLC), tristearin (TS) and palmitic acid (PA) having molar ratio 2:2:1 was modified by partially replacing SLC with ion pair amphiphile (NLCIPA), prepared by mixing equimolar aqueous solution of sodium dodecyl sulphate and hexadecyltrimethylammonium bromide. Hot homogenization followed by ultrasonication method was employed for the preparation of NLC and NLCIPA. Desirable SLC / IPA ratio for NLCIPA formulations were obtained by analyzing the interfacial behavior of the lipidic components in the presence of IPA at air-water interface. Considering the interfacial behavior and mutual miscibility, lipid compositions having SLC/IPA ratio equal to 2:3, 3:7 and 1:4 were selected for the preparation of NLCIPA. Analytical techniques like dynamic light scattering, differential scanning calorimetry, transmission electron microscopy, fridge fractured electron microscopy and atomic force electron microscopy assured higher stability of NLCIPA formulations compared to the conventional NLC and the NLCIPA with 30 mol% SLC was found to be optimum. Experimental evaluation of interfacial, solution phase and thermal characteristics of oleanolic acid (OA) loaded NLC and NLCIPA formulations indicated the accumulation of OA on the palisade layer and the drug acquisition was higher in NLCIPA than the conventional NLC. NLCIPA formulations were found even more promising to sustain the release of OA to a desirable extent. Higher cytotoxic activity for the OA loaded NLCIPA than the NLC was noted during the cytotoxicity studies on hepatocellular carcinoma, hepatocyte-derived carcinoma and colorectal carcinoma cancer cell lines. The NLCIPA formulations, therefore, can be considered as promising alternate to conventional NLC in improving the therapeutic efficacy of OA as the anticancer drug.